Abrasion resistant cast ferrous alloys

ABSTRACT

A NEW CAST IRON AND ARTICLE OF MANUFACTURE MADE THEREFROM IS PROVIDED HAVING UNUSUAL ABRASIVE RESISTANCE AND AN ORIENTED LAMELLAR STRUCTURE CONSISTING OF AT LEAST ONE MEMBER FROM THE GROUP PEARLITE AND BAINITE AND A COMPLEX CARBIDIC STRUCTURE CONSISTING OF BORON NITRIDES, BORON CARBIDES AND OTHER BORON COMPOUNDS.

United State e smofi Samuel A. Sholl, Clear-field, Pa., assignor toClearfield.

Machine Company, Clear-field, Pa. i

No Drawing. Filed Sept. 27, 1971, Ser. No. 183,876

Int. Cl. C22c 37/00, 37/100 US. Cl. 75123 CB ABSTRACT OF THE DISCLOSUREA new cast iron and article of manufacture made therefrom is providedhaving unusual abrasive resistance and an oriented lamellar structureconsisting of at least one member from the group pearlite and bainiteand a complex carbidic structure consisting of boron nitrides, boroncarbides and other boron compounds.

The present invention relates to cast ferrous alloys and particularly aunique ferrous alloy having an exceptional combination of physicalproperties including outstanding resistance to abrasion, air hardeningand 'Wear resistance. The alloy is of special utility in the manufactureof articles which are used in grinding or polishing or in handlingabrasive material such as sand, shot or the like.

In general, regular cast iron, with ladle additions of such elements aschromium, molybdenum, nickel and copper either singly or in combinationswith other elements are used to produce an improved abrasion or wearresistant cast iron. These elements will impart a matrix structurecontaining a portion of complex carbides, ferrite, pearlite, togetherwith flake or nodular graphite. The type or form of graphite dependsupon the process used in producing the alloy. In addition to theseelements cited above, the addition of increased manganese percentages isalso beneficial as an assist towards further improvement in the wearresistant properties. When the manganese content is increased above thatnormally contained in cast iron, range from about 0.30 to 1.00%, themanganese has the property of imparting to the ferrous alloys improvedwear resistance when in contact with granular hard mineral substances.As in all ferrous castings, the percentages of the elements mentionedabove are related to the thickness of the castings and the rapidity ofthe air quench as the castings are cooled below the criticaltemperature. Depending upon the gradient temperature, hard massivecarbides will be developed to a greater or lesser degree in the metalsmatrix structure. In addition, the reduction in the percentages ofcarbon and silicon will have a profound influence on the amount ofcarbide produced and will have a direct bearing upon the toughness orbrittleness of the metal to such an extent that the castings will becomeexcessively brittle and break upon the slightest rough handling. Inthese types of cast iron, the massive carbides are randomly orientedthroughout the matrix structure and do not have the tough resistance toabrasive wear to obtain satisfactory life, when exposed to mineralshaving a hardness of more than on the Mohrs hardness scale.

The present invention is based upon the discovery that the element boronwhen used in conjunction with other elements in proper amounts, inferrous alloys where free carbon is present, such as the cast ironswhich are either hypo or hyper eutectic, will produce a superiorabrasion wear resistant alloy iron that is superior in many aspects tothe present [family of cast irons of this type. In the ferrous alloy ofthe invention boron and manganese and other elements such as enumeratedabove, are added to the melt in sequence, so as to provide a family ofnodular and flake irons that will produce a directionally orientedmatrix structure consisting but not necessarily adhering to platecarbides of complex type and more or less alternating with pearlite orbainite.

ABRASION RESISTANT CAST FERR'QUS krioiis Patented June 4, 1974 It is anobjectof this invention to provide a ferrous :alloy of superior abrasionand wear resisting properties.

, shown.

The present invention provides an unique and novel ferrous productcontaining at least 40% carbon and silicon within the cast iron range,and at least 0.1% boron, and at least 0.30% manganese. Free carbon maybe in small amounts of vermicular, nodular, or flake form. The ratio ofthe complex carbides to pearlite remains in approximately 1 to 1proportions for all applications, but adjustments in elemental contentwill vary according to the metal thickness and mass involved. Thisstructure is obtained in the as cast condition. No heat treatment isrequired, a definite advantage over those requiring heat treatment toobtain the necessary properties.

Both manganese and boron have been used extensively in the founding art.But the combination of these two to produce the type of ferrous alloydescribed has not been known to be used. The use of elemental manganesein excess of approximately 1% often is conducive to producing gas holedefects in castings, caused, it has been postulated, by either molecularhydrogen or molecular nitrogen in cast iron.

With the addition of boron to the melt this problem of gas hole castingdefects has been eliminated, due probably to the boron reactingstoichiometrically with atomic hydrogn or atomic nitrogen to formcomplex boron hydrides and boron nitrides in the presence of the highenergy developed in the molten metal. The boron nitrides are exceedinglyhard and approach the diamond in hardness. Therefore, minute quantitiesof these boron compounds located in interstitial positions within thebody centered cubic structure of the ferrous metal materially assist inimparting increased resistance to abrasion and other wear resistingproperties. The interstitial compounds thus formed have the propertiesof true metals, and have the formula of the MX type.

The interstitial compounds, in addition to those described above, andincorporated into the cubic structure are other borides includingmanganese boride, ferrous borides, silicon boride, and boron carbides.These compounds are also extremely hard with hardness values lyingbetween diamond (10) Mohrs scale and Topaz (8). It is, therefore,probably these metallic compounds that cause the unique propertiesdescribed above. But in addition to this I have found that the alloy hasuniqueness of orientation of the carbides and nitrides alternating witha pearlitic, bainitic oriented matrix structure that also impartstoughness to the metal. The apparent alternation of these plates causesthese properties to occur, that is toughness in conjunction with wearand abrasion resistance.

This invention can perhaps best be understood by reference to thefollowing examples.

EXAMPLE I Muller wear plates for crushing large pieces of minerals suchas bauxite, kaolinite, quartz and calcined clay were made by castingfrom the following alloy composition:

the balance iron with usual impurities. These wear plates gave more thana 300% increase in wear life as compared with the previously used.ferrous alloy..having.abra-..- .platesiromarotary-mullet. The. resultingscreen life was sion and wear resistant properties.

EXAMPLE II n Plow scraper castings having a section size of l /z-f' andweighing approximately 60 pounds each were cast from an alloy of thecomposition:

Percent C 3.45 Si I 2.60 Mn 2 a 3.2 B 0.5 H 0.001 N 0.004

Percent Si 150-2.60 Mn 0.30-4.5

B O.l-1.0 H .00l-.002 N .001-.008

Chromium, molybdenum, nickel and copper may be present alone or togetherin small amounts with iron making up the balance of the composition.

A preferred somewhat narrower range of composition is:

Percent with the remaining materials as mentioned herein above.

EXAMPLE III Screen plates with discharge apertures varying from to A andsection sizes from to 1" and averaging 150 pounds in weight were castfrom the alloy of Example I. Abrasive materials were discharged throughthese in excess of 300% greatenthan that of the previously used plates.

In the foregoing specification I have set out certain preferredembodiments er this invention, however, it will be understood that itmay be otherwise embodied within the" scope "of the following claims.

1. A manganese containing cast iron composition having ,unus ualabrasive resistance" and an oriented lamellar matrix consisting of atleast one member from the group consistingpfp earl-ite andbainitealternating with a complex carbidic structure consisting of complexboron nitrides, boron c'arbides and other boron compounds consistingessentially of carbon about 2.50% to 3.60%, silicon about 1.50% to2.60%, manganese 0.3% to 4.5%, boron 0.1% to 1.0% and the balance ironwith usual impurities in ordinary amounts.

2. A cast iron composition as claimed in claim 1 wherein the alloyincludes small amounts of nickel, chromium, copper and molybdenum.

3. A cast iron composition as claimed in claim 1 wherein the carbon isabout 3.30% to 3.60% and the silicon is about 2.20% to 2.60%.

4. A manganese containing cast iron composition as claimed in claim 1wherein the carbon content is 3.4%, the silicon content is 2.4%, themanganese content is 3% and the boron content is 0.5%

5. A manganese containing cast iron composition as claimed in claim 1wherein the carbon content is 3.45%; the silicon content is 2.6%, themanganese content is 3.2% and the boron content is 0.5%.

References Cited UNITED STATES PATENTS 2,046,912 7/1936 Kormann 123 CB2,943,932 7/1960 White 75-123 CB 3,299,482 1/1967 Tache 75-123 CB2,224,448 12/1940 Schlumpt 75123 B 2,630,382 3/ 1953 Wasserman 75123 CB3,193,383 7/1965 Butler 75-123 3,253,907 5/1966 'Schwindt 75-130 HYLANDBIZOT, Primary Examiner v US. Cl. X.R. 14835

